Checking through the community, this is a recurrent problem. Flickering issues are usually related to the lighting setup, especially in combination with emissive materials, or working with Lumen and RTS at the same time. Play around with the brightness, emissive, and exposure levels, as well as making sure that your scene has either Lumen or RTX, not both.
As well, similr scenarios were encountered in the following threads, please check the solutions implemented on them: